Method of foaming polyvinyl chloride using an activator



United States Patent 3,394,090 METHOD OF FOAMING POLYVINYL CHLORIDE USING AN ACTIVATOR Dieter H. A. Hayer, Stuttgart, Germany, assignor to G. Siegle & Co. GmbI-I, Stuttgart, Germany No Drawing. Filed May 11, 1964, Ser. No. 366,654 1 Claim. (Cl. 260-25) For pressureless production of foam products on the basis of high polymers, especially of polyvinyl chloride and its mixed-polymerizates, there are employed propellants, as, for example, azodicarbonamide and benzene sulphonehydrazide. In order to be able to carry out this process also at lower temperature it is customary to add to these propellant-added mixtures also an activator or so-called kicker. For obtaining a sufiicient lightand heat-stabilization there is also added to these mixtures a commercial stabilizer.

As activators for polyvinyl chloride and similar high polymers there are usually employed basic lead salts, as, for example, lead carbonate, lead sulphate, lead phthalate, and similar compounds, but also zinc compounds, as, for example, Zinc oxide, all of which give a comparatively good kicker-effect. But the heatand light-stabilization obtained with these products is insufficient for the majority of employment purposes. Moreover, the hithertoemployed products, because of the comparatively great covering ability, exhibit white-pigment characteristics, so that with the employment of such activators it is usually only in special cases that it is possible to obtain dark and deep colortones.

It has now been found that by the employment of salts of 'bivalanet metals and monocarboxylic acids there is obtained not only an excellent kicker effect but at the same time also a very good heatand light-stabilization. The acids employed are preferably aliphatic aromatic and mixed aliphatic-aromatic monocarboxylic acids with a C-number of 6-l4.

Good results are obtained with alpha-phenylbutyric acid, p-tolylic acid, p-chlorobenzoic acid and trichlorobenzylic acid. There are preferably employed aromatic carboxylic acids which contain one or more alkylor aryl-groups as well as halogen-groups. As metals there find employment preferably cadmium and lead.

The advantages of the method of the invention can be seen from the following table, in which there is presented the activating and stabilizing efiect of the products of the invention in comparison with a commercial activator and a commercial stabilizer at a foaming carried out at 160 C. and a furnace test carried out at 180 C. As the commercial activator there was employed zinc oxide, and as the commercial stabilizer, Nuostabe V-979. The numerical values give the foaming duration in sec onds respectively the duration of the heat treatment until a clearly beginning discoloration in minutes.

3,394,090 Patented July 23, 1968 ice Foaming Beginning of Duration Discoloration in Seconds After Minutes Commercial activator 160 10 Commercial stabilizer 950 45 Cadmium salt of alphaphenylbutyric acid. 158 40 Cadmium salt of methylbenzoic acid 214 45 Lead salt of methylbenzoic acid 165 45 Cadmium salt of trichlorophenylaectic acid 229 35 Cadmium salt of alpha-ethylhexanoic acid u 200 45 The foaming duration was determined in the following manner: 15 grams of dioctylphthalate, 15 grams of azodic-arbonamide, and 10 grams of a kicker of the invention were maintained in an oil bath at a temperature of 160 C. At this there split off gases, which were captured and measured. After the times stated in the above table the gas evolution was ended. At the furnace test carried out for determining the heat stability the following recipe was employed: parts of polyvinyl chloride (produced according to the suspension method), 30 parts of dioctylphthalate, 1 part of lubricant (commercial monooleate), and 1 part of product according to the invention.

The quantity of the activator according to the invention added to the aforementioned substances may be between 0.5 and 10% of the total quantity of the polymer.

A foam product produced according to the invention at low temperature without pressure exhibits the following composition: parts of polyvinyl chloride or polyvinyl chloride-mixed polymerizates; 60* parts of softener, for example, dioctylphthalate; 4 parts of propellant, for example, azodicarbonamide; 1 part of a product according to the invention.

What is claimed is:

1. In a method of preparing foam articles from a mixture comprising (a) polyvinylchloride, and (b) a heat decomposable propellant therefor containing a nitrogento-nitrogen bond wherein the mixture is heated to an elevated temperature at which the propellant releases gas and the polyvinylchloride is foamed thereby, the improvement which comprises simultaneously activating the propellant and stabilizing the polyvinylchloride by admixing 0.5-10 parts by weight of an activator with each 100 parts by weight of the polyvinylchloride prior to the foaming thereof, the activator consisting of at least one salt of a divalent metal and a monocarboxylic acid containing one aryl group selected from the group consisting of the lead and cadmium salts of alpha phenylbutyric acid, met-hylbenzoic acid, trichlorophenylacetic acid, p-chlorobenzoic acid and mixtures thereof.

References Cited UNITED STATES PATENTS 3,197,423 7/ 1965 Ackerman 260-25 MURRAY TILLMAN, Primary Examiner.

M. FOELAK, Assistant Examiner. 

1. IN A METHOD OF PREPARING FOAM ARTICLES FROM A MIXTURE COMPRISING (A) POLYVINYLCHLORIDE, AND (B) A HEAT DECOMPOSABLE PROPELLANT THEREFOR CONTAINING A NITROGENTO-NITROGEN BOND WHEREIN THE MIXTURE IS HEATED TO AN ELEVATED TEMPERATURE AT WHICH THE PROPELLANT RELEASES GAS AND THE POLYVINYLCHLORIDE IS FOAMED THEREBY, THE IMPROVEMENT WHICH COMPRISES SIMULTANEOUSLY ACTIVATING THE PROPELLANT AND STABILIZING THE POLYVINYLCHLORIDE BY ADMIXING 0.5-10 PARTS BY WEIGHT OF AN ACTIVATOR WITH EACH 100 PARTS BY WEIGHT OF THE POLYVINYLCHLORIDE PRIOR TO THE FOAMING THEREOF, THE ACTIVATOR CONSISTING OF AT LEAST ONE SALT OF A DIVALENT METAL AND A MONOCARBOXYLIC ACID CONTAINING ONE ARYL GROUP SELECTED FROM THE GROUP CONSISTING OF THE LEAD AND CADMIUM SALTS OF ALPH PHENYLBUTYRIC ACID, METHYLBENZOIC ACID, TRICHLOROPHENYLACETIC ACID, P-CHLOROBENZOIC ACID AND MIXTURES THEREOF. 